The present invention relates to an optical module and more particularly, the optical module that is useful in cost reduction and improvement of reliability.
Recently, it is strongly required to reduce the cost of an optical module to realize the optical subscriber network. To answer the requirement, a lot of studies have been reported for simplifying the alignment process between an optical device and an optical fiber and decreasing number of the parts of an optical package. In connection with this, for example, in xe2x80x9cThe Journal of Japan Institute for Interconnecting and Packaging Electronic Circuits, Vol. 10, No.5, pp302-305 and pp325-329 (1995), it is described passive alignment and packaging technology for optical devices.
Optical receiver modules are key devices in the optical communication system. It is composed of several components such as optical semiconductor devices, an optical fiber and/or an optical waveguide, lens for the optical coupling, electronic devices, substrate, lead pins, and package.
Regarding the packaging, the hermetic sealed metal or ceramic package is described in xe2x80x9cThe Journal of Japan Institute for Interconnecting and Packaging Electronic Circuits, Vol. 10, No.5, pp320-324 (1995)xe2x80x9d. The MCF (Multilayer Ceramic Frame) package that has both good frequency response equal to metal package and mass productivity equal to ceramic package is also described.
The plastic resin package is expected to be the substitution of these packages because the plastic package is suitable for low cost mass production, but the plastic package has high transmission of moisture, which is general weak point nevertheless. To improve the problem, the encapsulation with transparent organic materials or grass lid covering of optical semiconductor devices have been proposed as simple sealing methods.
However, the plastic package has another weak point; the package is more transmissive to electromagnetic wave than that of metal package and ceramic package, and is more sensitive to EMI (Electromagnetic Interference). Though the problem can be improved by attaching electromagnetic shield to the module, the conventional sealing method with wholly covered metal is not suitable for practical use, because the cost is high. Therefore, it is the subject to realize electromagnetic sealing keeping the plastic package""s advantage in low cost.
It is an object of the present invention to provide an optical module with plastic package and to improve the problem of the electromagnetic interference.
It is another object of the present invention to provide an optical module having simple structure and to improve the problem of the electromagnetic interference.
The present invention has invented by paying an attention to the point that lead frame is a component of an optical module. Lead frame is a thin metal plate and composed of the plate on which devices and a substrate are mounted and lead pins for input/output the electric signal. Lead frame has the function of holding a substrate, heat radiation, and connector. The invented optical module is using the lead frame as a part of electromagnetic shielding.
The object of our invention can be achieved by using an optical module comprising a lead frame molded by the first resin molded part, a substrate mounted on the lead frame with optical devices, the second resin molded part (the substrate is sealed by the first and second resin molded part.) and a electric conductive parts connected with the lead frame covering the substrate. According to the structure, the optical parts in the module are covered with the lead frame and the conductive parts; therefore, the optical parts are electromagnetic shielded. According to the invention, an optical module using plastic package and with electromagnetic interference free can be obtained.
Although metal parts, which provided between the first and the second packages, are useful for conductive parts, and, for example, metal plating layer formed on the second package is also useful for it. Moreover, fabricated conductive metal parts, which provided in inside of the second package and a fabricated conductive metal parts in order to cover outside of the second package are also useful.
The above object also can be achieved by using an optical module comprising a lead frame molded by the first resin encapsulating package, a substrate mounted on the lead frame, optical devices mounted on the substrate, and electric conductive parts connected with the lead frame. The substrate is inserted between the first resin molded package and the conductive parts. In the case, the conductive parts have the function of the second resin-molded package. The conductive parts are adjacent to a fiber holding component.
Moreover, the optical module of the present invention also has at least a lead frame, a substrate mounted on the lead frame, an optical module mounted on the substrate, a conductive parts electrically connected with the lead frame and covering or packing the substrate, and a resin molded package which molds at least the substrate and the conductive parts. Bending part of the lead frame can make the conductive parts.
The optical module of the present invention is manufactured by following steps: mounting optical devices on a substrate, mounting the substrate on the lead frame molded by the first resin molded package, covering the optical device with transparent resin, and fixing the second package having a conductive parts to the first package. The following method is also useful: mounting an optical device on a substrate, mounting the substrate on the lead frame, connecting a conductive parts for covering the substrate to the lead frame, and molding at least the substrate and the conductive parts.
According to the constitution described above, the optical module having plastic package, characteristics of electromagnetic interference free, and simple structure can be obtained.